The present invention relates to a novel process for preparing selectively 2,4- or 3,6-di-alkyl and di-aralkylphenol compounds which are very important as starting materials for loading materials of rubber, antioxidants, plasticizers, phenol resins or developers of the thermosensitive and pressure-sensitive recording sheets and so on.
As the methods for preparing the di-substituted phenol compounds, a method of alkylation and aralkylation on the phenol nucleus, or a method of transferation and a method of disproportionation generally are known.
In the alkylation and aralkylation on the phenol nucleus, it is known that hydrochloric acid, oxalic acid, phosphoric acid, p-toluenesulfonic acid, sulfuric acid, trifluoromethanesulfonic acid or alumina can be used as a catalyst according to Journal of the Colour Society, Vol. 17(1), p. 3-10, 1978, Spanish Pat. No. 336,838, Japanese Patent publication (Kokai) No. 48-86834, U.S. Pat. No. 3,290,389, French Pat. No. 1,484,640 and U.S. Pat. No. 3,290,392.
The product obtained by the above-mentioned references is only mono-substituted phenol or a mixture of mono-, di- or tri-substituted phenol and position isomers thereof. Namely, the di-substituted phenol compounds cannot be selectively produced by the catalysts used hitherto.
Further, it is well known that the amount of an olefin to a phenol compound have an effect on the composition of the resultant product. Using less than the theoretical amount of an olefin, however, the amount of the formed di-substituted phenol compounds are reduced, whereas by using more than the theoretical amount of an olefin, the poly-substituted phenol compounds are formed in large quantities and accordingly, the objective di-substituted phenol compounds are difficult to separate.
The methods of the transferation or disproportionation are described, for example, in Japanese Patent publication (Kokai) Nos. 60-255742 and 61-200934. According to such methods, at first poly-substituted phenol compounds are produced and then the obtained poly-substituted phenol compounds are converted to the di-substituted phenol compounds. As a result, the objective di-substituted phenol compounds are prepared by two steps, and cannot be satisfactorily obtained.
Such reaction product consists of a mixture of the various substituted phenol compounds and is considerably colored. Further, it is necessary to carry out more troublesome separation for the purification of the objective di-substituted phenol compounds. Consequently, the methods of the transferation or disproportionation have various disadvantages from the industrial viewpoint.
Therefore, in prerparing industrially useful di-substituted phenol compounds by means of the alkylation or aralkylation methods on the phenol nucleus, it has been desired to use catalyst which allows the reaction to perform selectively and by one step without causing the reaction of transferation or disproportionation.